What is Anaphylaxis?
- Anaphylaxis is an immediate, life threatening systemic reaction that occurs an exposure to a particular substance.
- It results from a type I hypersensitivity reaction in which release of chemical mediators from mast-cells results in massive vasodilation, increased capillary permeability, bronchoconstriction, and decrease peristalsis.
- It may caused by immunotherapy, skin testing, medications, contrast media infusion, insect stings, certain foods, or exercise.
- Prompt identification of signs and symptoms and immediate intervention are essential; the more quickly a reaction occurs, the more severe it tends to be.
- Complications include cardiovascular collapse and respiratory failure.
- Immediately asses airway, breathing, and circulation if presentation is severe, and intervene with cardiopulmonary resuscitation as appropriate.
- If presentation is less severe, assess vital signs, degree of respiratory distress, and presence of angioedema.
- Signs and symptoms include:
- Urticaria (hives), angioedema, pruritus, flushing.
- Laryngeal edema, bronchispasm, cough, wheezing, feeling of lump in the throat.
- Hypotension, tachycardia, palpitations, syncope.
- Nausea, vomiting, diarrhea, abdominal pain, bloating.
Therapeutic and Pharmacological Interventions
- Immediate treatment should include application of tourniquet above site of antigen injection (allergy injection, insect sting) or skin test site, to slow the absorption of antigen into the system.
- Epinephrine 0.1 to 0.5 mg (0.01 mg/kg) is injected into opposite arm subcutaneously (S.C) or I.M. may repeat every 15 to 20 minutes, if necessary, to cause vasoconstriction, decrease capillary permeability, relax airway smooth muscle, and inhibit mass cell mediator release.
- Subsequently, an adequate airway is established and hypotension and shock are treated with fluids and vasopressors.
- Bronchodilators are given to relax bronchial smooth muscle.
- Antihistamines, such as diphenhydramine and, possibly H2-histmaine blockers, such as ranitidine, may be given to block the effects of histamine.
- Corticosteroids are given to decrease vascular permeability and diminish the migration of inflammatory cells; may be helpful in preventing late-phase responses.
- Continually monitor respiratory rate and depth and breathe sounds for respiratory effort and effectiveness of ventilation.
- Monitor blood pressure using continuous automatic cuff.
- Monitor central venous pressure to ensure adequate fluid volume and to prevent fluid overload.
- Insert indwelling catheter and monitor urine output hourly to ensure kidney perfusion.
- Establish and maintain an adequate patent airway. If epinephrine has not stabilized bronchospasm, assist with endotracheal intubation, emergency tracheostomy, or cricothyroidotomy as indicated.
- Administer nebulized epinephrine and/or other bronchodilators, as ordered. Monitor heart rate (increased with bronchodilators).
- Provide oxygen by nasal cannula at 2 to 5 liters per minute or by alternate means, as ordered.
- Rapidly infuse I.V. fluids to fill vasodilated circulatory system and raise blood pressure. Titrate vasopressors based on blood pressure response.
- Remain responsive to the patient, who may remain alert but not completely coherent because of hypotension, hypoxemia, and effects of medication.
- When the patient is stable and alert, give a concise explanation of anaphylaxis and the treatment that was given.
- Keep family and significant others informed of the patient’s condition and treatment being given.
- Instruct the patient to read labels and be familiar with the name of the drug thought to cause a reaction.